Mosquito coils are coils of slowly burnable solid material that contain an insect control ingredient such as a repellent, an insecticide, or an insect growth regulator. When they burn, heat vaporizes (and thereby disperses) the insect control ingredient. Small amounts of smoke also help to disperse the insect control ingredient.
U.S. Pat. No. 5,447,713 discloses a mosquito coil having a conventional spiral configuration, and U.S. Pat. No. 3,754,861 teaches a mosquito coil having a match-like ignition tip containing potassium chloride as an oxidizer (albeit the tip does not contain any insect control ingredient). Also known are solid fumigants in certain other shapes. See e.g. U.S. Pat. No. 4,959,925.
Various compositions for such solid fumigants are known. For example, U.S. Pat. No. 4,144,318 teaches the use of allethrin, tabu powder, starches, wood powder, coco shell powder, and dye in mosquito coils, and U.S. Pat. No. 4,296,091 teaches the use of a perfume in a mosquito coil.
One drawback of prior art mosquito coils is that no provision was made to provide quick coverage for a room or other environment that previously had no insect control ingredient in it. Thus, the environment could not safely be used for an inconveniently long time.
Another drawback of the prior art coils is that they broke too easily during manufacture and handling.
A difficulty in trying to address such problems is that mosquito coils must be made so that they can be easily lit, yet they must burn at a very slow rate once lit so as to provide extended protection throughout the night. This places significant limitations on the shape and composition of mosquito coils.
It can be seen that a need exists for improved mosquito coils.